Math Problem Statement

Write the expressions for (f + g)(x) and (f · g)(x) and evaluate (f - g)(-2) for the functions f(x) = 2x^2 and g(x) = x + 4.

Solution

The problem involves two functions, f(x)=2x2f(x) = 2x^2 and g(x)=x+4g(x) = x + 4, and asks for the following:

  1. The expression for (f+g)(x)(f + g)(x),
  2. The expression for (fg)(x)(f \cdot g)(x),
  3. The evaluation of (fg)(2)(f - g)(-2).

Step 1: Finding (f+g)(x)(f + g)(x)

By definition, (f+g)(x)=f(x)+g(x)(f + g)(x) = f(x) + g(x).

Given:

  • f(x)=2x2f(x) = 2x^2
  • g(x)=x+4g(x) = x + 4

So: (f+g)(x)=2x2+(x+4)=2x2+x+4(f + g)(x) = 2x^2 + (x + 4) = 2x^2 + x + 4

Step 2: Finding (fg)(x)(f \cdot g)(x)

By definition, (fg)(x)=f(x)g(x)(f \cdot g)(x) = f(x) \cdot g(x).

So: (fg)(x)=(2x2)(x+4)=2x2(x+4)=2x3+8x2(f \cdot g)(x) = (2x^2) \cdot (x + 4) = 2x^2(x + 4) = 2x^3 + 8x^2

Step 3: Evaluating (fg)(2)(f - g)(-2)

By definition, (fg)(x)=f(x)g(x)(f - g)(x) = f(x) - g(x).

So: (fg)(x)=2x2(x+4)=2x2x4(f - g)(x) = 2x^2 - (x + 4) = 2x^2 - x - 4 Now, substitute x=2x = -2: (fg)(2)=2(2)2(2+4)=2(4)(2)=82=6(f - g)(-2) = 2(-2)^2 - (-2 + 4) = 2(4) - (2) = 8 - 2 = 6

Final Answers:

  1. (f+g)(x)=2x2+x+4(f + g)(x) = 2x^2 + x + 4
  2. (fg)(x)=2x3+8x2(f \cdot g)(x) = 2x^3 + 8x^2
  3. (fg)(2)=6(f - g)(-2) = 6

Would you like further details on any of the steps?

Here are 5 related questions you might consider:

  1. What is (fg)(x)(f - g)(x)?
  2. How do you evaluate (fg)(2)(f \cdot g)(-2)?
  3. What would the derivative of (f+g)(x)(f + g)(x) be?
  4. How does the function (fg)(x)(f \cdot g)(x) behave for large values of xx?
  5. What happens if you compute (f/g)(x)(f / g)(x)?

Tip: Always double-check your function evaluations by substituting carefully to avoid simple arithmetic mistakes.

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Math Problem Analysis

Mathematical Concepts

Algebra
Functions
Function Operations

Formulas

(f + g)(x) = f(x) + g(x)
(f · g)(x) = f(x) · g(x)
(f - g)(x) = f(x) - g(x)

Theorems

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Suitable Grade Level

Grades 9-10